Move downloads to a cache directory

- cleanup cache during apps first cold start
- Downloads now saved in cacheDirectory and moved to documents when verified complete
- Bring back download size to episode card
- Improve reading a files size if its a known downloaded file
- Added decimal to divisor in bytesToReadable for more accurate file size conversions

components/downloads/EpisodeCard.tsx

@@ -91,6 +91,7 @@ export const EpisodeCard: React.FC<EpisodeCardProps> = ({ item, ...props }) => {
           <Text className="text-xs text-neutral-500">
             {runtimeTicksToSeconds(item.RunTimeTicks)}
           </Text>
+          <DownloadSize items={[item]} />
         </View>
       </View>